Process of making sulfuric anhydrid.



"New TAT sTP -T NT OFFICE- MAX LE BLANC, OF GARLSRUHE, AND CONSTANTIN KRAUSS, OF HGCHST- ON-THE-MAIN, GERMANY,

ASSIGNORS TO FARBWERKE, VORM. MEISTER,

LUOIUS & BRUNING, OF HGCHST-ON-THE-MAIN, GERMANY, A CORPORA- TION OF GERMANY.

PROCESS O IVIIAKINGESIUJLFURIC ANHYDRID.

SBEOIFIGATION forming part of Letters Patent N 0. 726,076, dated April 21-, 1903.

' Application filed June 19, 1901. Serial No. 65,159. (No specimens.)

To (tZZ whom it may concern: I

Be it known that we MAX LE BLANC, residing at Oarlsruhe, and OONSTANTIN KRAUSS, residing at Hochst-ou-the-lvlain, Germany, citizens of the Empire of Germany, have invented certain new and useful Improvements in Processes of Making Sulfuric Anhydrid, of which the following is a specification.

The speed of every chemical action whether .0 endothermic or exothermic, as well as the final equilibrium, depend on the temperature of the sphere ofaction, or, in other words, under equal conditions a precise reaction velocity and equilibrium'are inherent to every temperature. As regards the dependency on temperature, it is known from the teachings of thermodynamics confirmed by numerous experiments that the reaction velocity increases with a 'rise' of temperature and that the equilibrium varies with rise of temperature in such a manner that those products increase which are formed with absorption of heat. These facts have been extensively applied knowingly and unknowingly in chemical industry, especially as regards organic chemistry. Instances are the acceleration of chemical reactions by heating and boiling and the moderation of them by cooling.

Manufacturers of inorganic chemicals have 0 been paying greater attention of late to this field of physical chemistry. This is especially the case in the manufacture of sulfuric anhydrid by the contact process. Whereas formerly no particulars were given in patent 3 5 specifications and the special literature as to the temperature inside the contact-chamber or there was used merely the ambiguous expression dull red heat, the English Patent No. 3,166'of 1888 for the first time distinctly 4o speaks ofthe temperature having to be carefully regulated in the contact ch'amberj The inventor, however, omitted to give exact particulars'as'to temperature and merely says at or below a dull red heat. This idea of regulating the temperature in the contactchamber is again to be found in German Patent No. 118,932 and English Patent No. 285

of 1899, Where it is technically applied in the prodnctionlof sulfuric anhydrid.

The object to be attained is the greatest go reaction velocity accompanied by the greatest yield of sulfuric anhydrid. Asuperficial observation, however, shows that a combination of these two factors in the manufacture of'SO is hardly" possible with the present mode of Working. I Of course the reaction velocity may be increased at will by a rise of temperature; but then the equilibrium between SO ,.O, and S0 is' also upset, as alreadysaid, in the sense that SO decomposes into S0 and 0. Experiments have undoubtedly confirmed this conclusion. It is well known that the combination SO +O to form S0 is possible witha satisfactory technical yield only within certain limits of temperature, whereas at a temperature of about 400 centigrade the reactioniis almost quantitative. The condition of equilibrium between 80,, O, and SO changes with the rise of temperature to the disadvantage of the formation of S0 and at about 500 centigrade a yield'of only about eighty-five to ninety per cent., and at about 530 centigrade of about seventy-five to eighty per cent. of S0 is obtained from the S0 employed. v

Further experiments have shown that the increase of the reaction velocity is surprisingly great. Thus in the presence of finelydivided platinum as catalytic agent at about 500? centigrade it is believed about twenty times as great as at 400 centigrade, A and at higher temperature it increases sti I more. The same unit of platinum which is. capable in the unit of timeat 400 centigradi; to transform almost quantitatively the S0 of a given limited quantity of pyrites-burner gases a, that even the smallest excess would not be 'transformed)'for instance, gases of about seven-volume per cent. of S0 and nine-volume per cent. of Ois also capable after our experiments in the same unit of time and at about 500 centigrade to transform about ninety per cent. of the S0 contained in twenty'times the quantity of pyrites-burner gases of the same compositioninto SO thatis to say, a contact mass, for instance, which in a given time is capable of inducing the oxidation of one hundred parts of SO to S0,. converts in the same time, according to our experience, at about 500 centigrade about twenty times ninety, equaling eighteen hundred parts, of SO to SO -that is, about eighteen times as much as at the lower temperature. At higher temperature the conditions are still more favorable. temperature of 500 centigrade the quantity oEpyrites-burner gases brought upto the equipoise (ninety per cent. S0 ten percent. S0 is twenty times greater than at a temperature of 400 centigrade, (one hundred per cent. 50,, no per cent. S0 The production of S0 is a resultant of velocity and temperature of the gases. At a temperature of 400 centigrade for one kilo of platinum-asbestos six liters per minute of pyrites-burner gases are brought up to the equipoise, whereas at a temperature of 500 centigrade one hundred and twenty liters per minute of the same gas mixture and the same quantity of catalytic are brought up to the equipoise, (ninety per cent. 80,, ten per cent. S0 From this fact, ascertained by experiment, it follows that really great reaction velocities first begin at temperatures at which the percentage in the yield of SO decreases, although a specially good catalytic agent, such as finely-divided platinum, may have been employed, and that a combination of high reaction velocity and high yield is not attainable so long as the entirecohtact-chamber is kept at the same temperature, as has been the case hitherto.

The present invention relates to improvements in the manufacture of sulfuric anhydrid by the method in question, whereby the catalytic process in the contact-chamber is first allowed to take place ata high temperature and then at a low one. In the first zone of reaction the temperature is kept so high that a great part of S0 is oxidized into SO in consequence of the great reaction velocity. The gases are then cooled to about 400 centigrade and allowed to pass the second contact zone at this lower temperature, where the rest of the S0 is oxidized, for considering the small quantities of SO still remaining the reaction vclocitysuffices at this lower temperature.

gp 'lhe accompanying drawing illustrates an apparatus adapted for carrying on the new process.

In the drawing, A indicates the first contact-chamber, and B the second. C is a pipe connecting said chambers, said pipe being exposed, as shown, so as to permit the radiation of heat therefrom. The gases SO +O enter A at a, pass upwardly through the successive layers (2 of contact material, which has a temperature of approximately 500 centigrade, and are in part converted into 80,. The mixture of S0 and unconverted SO +O passes through pipe 0 to chamber B At a' anddownwardly through the layers 1; of contact material therein to the outlet (1, from which the product issues. The contact-chambers may be maintained at any desired temperature by any suitable source of heat arranged in the spaces 6 e at the lower portion of the same.

As regards the technical application of this new process, two manners of obtaining the desired result may be described. Before the single contact used hitherto a second smaller contact may be inserted, in which case the reacting gases are first allowed to pass the.

smaller contact-for instance, at 530 centigrade. The reaction velocity here is so great that a considerable part of the S0 is rapidly oxidized to 80,. About seventy-five per cent. of the S0 present is here converted into 80,. Then the gases issuing from this contactchamber and still containing about twenty-five per cent. are indirectly cooled to about 430 centigrade by a set of pipes or directly inside the apparatus by mixing the hot reacting gases with 'cold gases which have no influence on the reaction, and the gases thus cooled are allowed to pass through a second contact-chamber at this temperature, where nearly all the rest of the S0 is oxidized. The eifect of course is the same, and the apparatus merely a complication if instead of two, three, or more contact-chambers with successively lower temperatures are inserted, so that the gases arecaused to combine in the first contact at about 530 centigrade and in the last at about 430 centigrade. A second technically convenient method is to enlarge the contact-chamberand to gradually cool the gases entering at about 530 to about 430 centigrade at their exit. In this case also one of the above-mentioned methods of cooling is used, and the eifect is the same, but the apparatus more complicated, if two or more enlarged contacts are used.

The rate at which the gases in the foregoing example traverse the contact chambers or chamber is greater than that of the methods employed hitherto. This is due to the diminution of the contact itselfthat is to say, the reaction being more rapid in consequence of the high temperature the gases need not stay so long in the contact-chamber, which, again, permits the employment of a considerably smaller contact surface or substance while obtaining the same quantity of $0,. In our process the contact-chamber is much smaller and the gases pass the same far more rapidly than in the case of a larger contact-chamber. In the same time, therefore, and with the same quantity of contact mass the multiple quantity of gas converted is greater than was hitherto possible in a satisfactory manner.

For the purpose of this new process for manufacturing anhydrid and in view of the high temperature possible in the first zone of reaction the catalyzing substances available in the contact process were examined and the following results were obtained: 1. The metals of the platinum group. 2. The oxids and sulfates of Fe, Cr, Ni, Co, Mn, Mr, Cu. 3. The oxygen compounds of Al, Be, Zr, Ce, Di, La, Th, Ti, Si, and of nearly all rare metals. 4.. Mixtures of No. 1 with one or more substances of Nos. 2 and 3. 5. Mixtures of two or more of the substances mentioned under Nos. 2 and 3.

It was found that whereas the catalyzing agents referred to under Nos. 1 and 4 prove to be efficacious already ata low temperature favorable to the formation of S0 the agents mentioned under Nos. 2, 3, and 5 are only efiicacious at high temperatures favorable to the reaction velocity, but unfavorable to the yield of S0 Therefore in the above example, one of the catalyzing agents mentioned under 2 to 5 may be substituted for the expensive platinum in that part of the contactchamber which is to be worked at high tem-.

tity of SO than has hitherto been obtained without any additional important cost and accompanied by an almost quantitative yield from the S0 gases treated.

Having thus described our invention, what we claim is- The herein-described process of obtaining SO from gases containing approximately seven per cent.of S0 and nine per cent. of O by means of the contact method, which consists in conducting the gas mixture through a first portion of contact substance at a temperature of approximately 500 centigrade and of approximately one hundred and twenty liters of pyrites-burner gases per kilo platinum-asbestos, and then directly conducting the resulting gas mixture at the samespeed through a second portion of contact substance at a temperature of approximately 400 centigrade, substantially as set forth.

In testimony that we claim the foregoing as our invention we have signed our names in presence of two subscribing witnesses.

MAX LE BLANO.

CONSTANTIN KRAUSS. Witnesses as to Max Le Blane:

JACOB ADRIAN, H. W. HARRIS. lVitnesses as to Constantin Krauss:

JEAN GRUND, CARL GRUND. 

